Winnipeg can use old malathion pending tests: Health Canada

Winnipeg can use its years-old malathion supply to kill nuisance mosquitoes if laboratory tests show the impurity content of the insecticide falls within acceptable standards, a City of Winnipeg spokesperson says.

Winnipeg could get green light to use its old supply of the mosquito killer

Malathion use in Winnipeg is on hold for nuisance mosquitoes pending test results. (turkletom/Flickr cc)

Winnipeg can use its years-old malathion to kill nuisance mosquitoes if laboratory tests show the impurity content of the insecticide falls within acceptable standards, a City of Winnipeg spokesperson says.

Health Canada's Pest Management Regulatory Agency (PMRA) told the city they will not object to use of malathion more than a year old if the isomalathion content of the malathion meets specifications such as those laid out by the World Health Organization.

The city is in the process of having its current stock of malathion tested for isomalathion content.

Earlier on Friday, Manitoba Health said it obtained permission from Health Canada to use the pesticide to control West Nile virus even though most existing stockpiles have been stored for more than one year.

CBC's I-Team informed the City of Winnipeg it is now illegal to store malathion for more than one year. Unbeknownst to the city's insect control branch, federal pesticide regulators changed the product label.

This effectively sidelined malathion as a pesticide, given that municipal stockpiles were purchased in 2007 and 2009 and provincial supplies date back to 2008. Provincial officials then contacted Ottawa for clarification.

On Friday, provincial officials said Ottawa has agreed to allow malathion fogging if West Nile presents a public-health risk. But first, the province must send samples of its stockpile to a laboratory in Ontario to ensure the pesticide has not degraded into a more harmful form.

"The Pest Management Regulatory Agency has advised Manitoba Health, Seniors and Active Living that the province's stockpile of malathion (which has been in storage for more than one year) can be used in the case of a public health emergency, providing test results show isomalathion levels are within accepted standards," a spokeswoman for Manitoba Health said in a statement.

Pending test results, the City of Winnipeg can now possibly use its stockpiles of malathion to kill mosquito species such as Aedes vexans, which are not known to transmit diseases to people.

A different species, Culex tarsalis, is a West Nile virus vector.
Malathion fogging could resume if impurities in Winnipeg's supply fall within acceptable standards, says city spokesperson. (CBC)

Winnipeg insect-control superintendent Ken Nawolsky said since the city does not fog for mosquitoes every year, it tends to hold on to supplies of the pesticide. The manufacturer doesn't even make it every year, he said.

The city had planned to end malathion use next year and switch to DeltaGard, a more expensive but less controversial fogging agent. DeltaGard is approved for use in the U.S. and is awaiting a green light in Canada.

"Winnipeg and other municipalities that do currently use malathion are in the same boat right now," Winnipeg Mayor Brian Bowman said.

The mayor said he's looking forward to the end of malathion use — but believes Winnipeggers want nuisance mosquito fogging to continue. Winnipeg's summers are short, he said.

Nawolsky said Winnipeg would have to engage in extensive public consultations before it considers an end to fogging for nuisance mosquitoes.